Oceanic Gas Hydrate Instability and Dissociation in Response to Climate Change

Authors: Moridis, George (speaker), and Reagan, Matthew, Lawrence Berkeley National Laboratory

Venue: American Geophysical Union fall meeting, San Francisco, CA, December 10-14, 2007 (http://www.agu.org/meetings/fm07/ [external site]).

Abstract: Paleo-oceanographic evidence has been used to postulate that methane from oceanic hydrates may have had a significant role in regulating past global climate, implicating global oceanic deposits of methane gas hydrate (clathrate) as the main culprit for a remarkably rapid sequence of global warming effects that occurred during the late Quaternary period. However, the behavior of contemporary oceanic methane hydrate deposits subjected to rapid temperature changes—such as those predicted under future climate change scenarios—is poorly understood, and existing studies focus on deep hydrate deposits under equilibrium conditions. Project researchers simulated the dynamic response of several types of oceanic gas hydrate accumulations to temperature changes at the seafloor and assessed the potential for methane release into the ecosystem. The properties of benthic sediments; the saturation, stability, and distribution of the hydrates; the ocean depth; the seafloor temperature; and the effects of biogeochemical activity were considered. The results suggest that while many deep hydrate deposits are indeed stable under the influence of rapid seafloor temperature variations, shallow deposits, such as those found in arctic regions or in the Gulf of Mexico, can undergo rapid dissociation and produce significant carbon fluxes over a period of decades. These results may be used to provide a source term to regional or global climate models to determine the impact of gas hydrate deposits on global climate.

Related NETL Project
The proposed research of the related NETL project FWP-G308 , “Numerical Studies for the Characterization of Recoverable Resources from Methane Hydrate Deposits,” is to develop and maintain a reservoir model that simulates the behavior of hydrate-bearing geologic systems and evaluates appropriate hydrate production strategies for both permafrost and marine environments, including thermal stimulation, depressurization, and dissociation induced and/or enhanced by inhibitors (such as brines and alcohols).

NETL Project Contacts
NETL – Kelly Rose (Kelly.Rose@netl.doe.gov or 304-285-4157)
LBNL – George Moridis (gjmoridis@lbl.gov or 510-486-4746)